One of the problems in cardiac bypass surgery is that when the patient's blood has been fully diluted in a bypass circuit with priming solution, addition fluid and cardioplegia solution, the hematocrit has dropped to well under normal values. Since the patient cannot take back his own blood volume and the circuit volume, much of this diluted blood and the patient's blood cells and proteins are left in the oxygenator, heat exchanger and tubing. Recently, a high ultrafiltration hemodialyzer has been used to concentrate this blood by removal of water so that a reasonable volume of the valuable blood constituents can be given back to the patient. In this operational mode, a dialyzer is used only as an ultrafiltrator so that no dialysis solution flow is required. Ultrafiltration is achieved by drawing a vacuum on the dialysate compartment. Sometimes a blood pump is used, but often a tap is made in the circuit downstream of the bypass circuit arterial pump or venous pump in the oxygenator. Thus the circuit and ultrafiltration unit must be primed without a pump.
Dialyzers may require the rinsing of both the blood compartment and the dialysate compartment to prepare the dialyzer and to guard against the possibility of a hypersensitivity reaction in the patient. Of course the rinsing solution must be discarded.
The present invention is particularly applicable to any type of ultrafiltration unit, including a hemoconcentrator, a dialyzer, a diafilter, etc. Such ultrafiltration units generally include an ultrafiltration membrane which separates a blood compartment from an ultrafiltrate compartment. When a dialyzer is used as an ultrafiltration unit, the dialysate compartment of the dialyzer becomes the ultrafiltrate compartment.
It is an object of the present invention to provide a system for priming an ultrafiltration unit without requiring a pump in the blood line.
Another object of the present invention is to provide a system for priming an ultrafiltration unit with a provision for automatically discarding the primng solution without disconnection or reconnection of the blood set.
A further object of the present invention is to provide a system for priming an ultrafiltration unit, enabling the priming and rising of both the blood compartment and the ultrafiltrate compartment, at prescribed flow and volume rates and with an automatic discard of the priming and rinsing solution without disconnection or reconnection of the blood set.
By avoiding the necessity of disconnecting or reconnecting the blood set before, during or after priming and/or rinsing, the sterility compromise concomitant with disconnection or reconnection is obviated.
Other objects and advantages of the present invention will become apparent as the description proceeds.